Globally, the largest environmental impact of agriculture is the use of land for pasture. More pasture is used to raise cattle than all other domesticated animals and crops combined. According to World Wildlife Fund estimates, every year, an area of the world's rainforest larger than New York State is destroyed to create grazing land.

Cattle feeding operations pose another significant environmental threat. About 1.4 billion metric tons of solid manure are produced by U.S. farm animals each year - 130 times the quantity produced by people. That amounts to 100,000 metric tons of manure per minute. This figure includes pigs and chickens as well as cattle, but cattle are the single largest source. The manure creates methane, a potent global warming gas. It also leaks into the groundwater, causing major pollution problems.

In addition, two-thirds of the beef cattle raised in the U.S. are fattened up using hormones like steroids, testosterone and progesterone. When these are excreted, they have the potential to pollute drinking water. The European Union bans beef from the U.S. because it contains growth hormones.

Chickens, turkeys, and pigs create similar environmental problems when they are raised in industrial feedlots.

Some "farm-raised" seafood, especially salmon and shrimp, can also endanger the environment. Producing one pound of farm-raised salmon or shrimp, for example, requires two to three pounds of wild fish for feed. The waste from fish farms can pollute coastal waters . And if farmed fish escape into the wild, they can threaten the survival of native fish.

Some varieties of fish, like tuna and swordfish, are dangerous especially for pregnant women and children, due to the high level of toxins they contain.

Fish and shellfish in the wild are being caught to excess and some, to the point of extinction. The cod fishery in the North Atlantic has already collapsed due to overfishing.

Dollars & Sense Options

Eat more organic fruits and vegetables. For specific benefits, see Choose Organic.

Buy local. Check at your local farmers market, food coop, and natural foods store. You may be able to buy chicken, beef and pork that's raised, packaged and sold within a hundred miles of your kitchen. Advantages? You'll be dealing with farmers whose smaller operations allow the animals to graze freely (also called "free range") and without antibiotics or hormones. Here's a good comparison between cattle allowed to graze freely and those fattened up on feedlots.

Choose fish that are low in mercury and other toxins, and don't face extinction from overfishing.

About Fish

White-fleshed fish are generally lower in fat than any other source of animal protein. Oilier fish contain generous quantities of omega 3s, the "good" fats that bolster the human diet, without the "bad" omega-6 fats red meat deliver.Omega-3s keep your heart and blood vessels healthy, may alleviate symptoms of depression and rheumatoid arthritis, and offer a variety of other health benefits.

The problem is that many fish are contaminated from heavy metals like mercury and lead, industrial chemicals like PCBs, and pesticides like DDT and dieldrin. These contaminants enter the water in several ways: from factory discharges, runoff from farms and lawns, and air pollution that falls into lakes, rivers, streams and the sea from sources like power plant cooling towers and automobile exhaust tail pipes. Fish can absorb these toxins in their skin, organs and fatty tissue.

Over time, the more toxin-laden fish you eat, the more contaminants can build up in your body. Health problems may include various birth defects and even cancer. According to Environmental Defense, it can take 5 years or more for women in their childbearing years to rid their bodies of PCBs, and 12-18 months to significantly reduce our body burden of mercury. Mothers who eat contaminated fish before becoming pregnant may have children who are slower to develop and learn. Developing fetuses are exposed to stored toxins through the placenta. Women beyond their childbearing years and men face fewer health risks from contaminants than children do.

You've probably heard the most about mercury in canned tuna. Both the Environmental Protection Agency and Environmental Defense recommend that adults and children limit consumption of canned white tuna, which consists of albacore, a large species that accumulates moderate amounts of mercury.

Canned light tuna usually consists of skipjack, a smaller species with approximately one-third the mercury levels of albacore. Therefore, Environmental Defense only recommends that young children (ages 0-6) limit their consumption of canned light tuna. However, recent news reports suggest that some canned light tuna actually contains yellowfin tuna, a species that is similar in size and mercury content to albacore. These products are sometimes (but not always) labeled 'gourmet' or 'tonno', and their consumption should be limited by adults and children. Overall, it's best to exercise caution in how much tuna you (or especially your children) consume.

Fish that are caught or farmed in an ecologically sound manner and thus are low in contaminants include wild salmon from Alaska (fresh, frozen and canned), Atlantic mackerel and herring, sardines, sablefish, anchovies, farmed oysters and tilapia.

You can learn more about your Best and Worst Seafood Choices from Environmental Defense's Oceans Alive website.

The Monterey Bay Aquarium's Seafood Watch regional guides contain the latest information on sustainable seafood choices available in different regions of the U.S. "Best Choices" are abundant, well managed, and fished or farmed in environmentally friendly ways. Seafood to "Avoid" are overfished and/or fished or farmed in ways that harm other marine life or the environment. You can view the guides online or download a pocket-size version.

You can also check in with the Marine Stewardship Council, a non-profit organization set up to protect fish from over-fishing. Your dollars can make a difference by buying seafood that's carefully harvested so that fish like cod and rockfish, whose populations have been severely depleted, stay alive. Look for seafood sold under the Marine Stewardship Council label.

If you want some help when you shop, Environmental Defense has prepared this handy Pocket Seafood Selector you can print out and keep in your wallet.

If you don't want to eat fish but you want the benefit of fish oil supplements, you still need to worry about the same contaminants showing up in the oil. Capsules should be made from purified fish oil. Here's more about fish oil supplements and the results of an Environmental Defense survey on the safest supplements to buy.

To find locally-produced meat and poultry, plug your zipcode in to this map managed by Local Harvest and the Food Routes Network. You'll find nearby farmer's markets, direct-sell farmers, and whole foods markets where you can buy beef, chicken and pork that's hormone and antibiotic free.

We have the benefit of living just a few blocks from a wonderful farmers market that's open all year long. Most of the time, we can get some variety of fresh fruits and vegetables, plus beef from a small farm, fresh eggs from free-range hens, and even artisan cheeses that are made in small, "home made" batches. My parents in southeastern Michigan have no option like this. Whenever I visit, I realize what a luxury it is to be able to buy such healthy food locally. My son is the only one of the four of us who prefers meat to chicken or fish; I'll occasionally serve him beef when the rest of us have seafood or poultry. We also eat a lot of veggies, eggs, fruits, and some pasta. I really like knowing that our food is fresh; I especially feel good that it's not pumped full of hormones and other chemicals. It just feels safer to cook, serve and eat! Plus, I like talking to the people at the market who raise my food. It connects me to the land in a way that that's missing when I simply buy a package of food wrapped in plastic from the grocery store. That being said, my kids aren't yet sold on the environmental benefits of buying local, or "free range" vs. industrial beef or poultry. They just know what tastes better. For now, that's ok with me.